Enzymes: How Cells Promote Chemical Activities - 111 



must be regarded as master enzymes in the 

 cell. Not only do they perpetuate themselves 

 by an intricate kind of autocatalysis, but also 

 the}' govern the production of the enzyme 



proteins, utilizing the RNA constituents of 

 the cell to transmit a precisely coded set of 

 instructions (Chap. 27). 



TEST QUESTIONS 



1. Define the term catalyst and carefully de- 

 scribe any typical example of catalysis. 



2. What is an enzyme? How and why are en- 

 zymes important in every cell and every 

 organism? 



3. Name any four enzymes and specify the 

 chemical reaction that is catalyzed by each. 



4. Distinguish between enzymes and inorganic 

 catalysts, on the basis of: 



a. chemical composition 



b. stability at higher temperature 



c. specificity of action 



d. sensitivity to hydrogen and other ions 



5. Is there any known relation between en- 

 zymes and vitamins? Explain. 



6. Is there any known relation between en- 

 zymes and genes? Carefully expfain. 



7. Provide appropriate examples of: 



a. one or more enzymes that are substrate 

 specific 



b. two enzymes that are specific in rela- 

 tion to some particular chemical con- 

 figuration. 



8. Summarize the evidence from which it may 



be concluded that all enzymes, in essential 

 part, are of protein composition. 

 9. Define and explain: 



a. catalytic site 



b. catalytic fit 



c. enzyme-substrate compound 



d. energy of activation 



e. the mitochondrial enzyme team 



f. competitive inhibition of enzyme ca- 

 talysis 



10. Explain why certain enzymes lose their power 

 of catalysis when they are extracted from the 

 protoplasm. 



11. Describe and explain the changes in the 

 speed of reaction in the following cases: 



a. the decomposition of H..O., in the 

 presence of Mn0 2 at 30°, 40°, and 

 50° C 



b. the decomposition of H 2 Oo in the 

 presence of catalase at 30°, 40°, and 

 50° C 



12. How might the oxygen consumption of a 

 man be affected by (a) fever and (b) a sub- 

 normal temperature? Explain. 



FURTHER READINGS 



Cellular' Physiology and Biochemistry, by 



William D. McElroy; Englewood Cliffs, N. J., 



1961. 



Genes, Enzymes, and Inherited Diseases, by 



H. E. Sutton; New York, 1961. 



"Enzymes," by J. Pfeiffer, in The Physics and 

 Chemistry of Life, a collection of articles from 

 Scientific American; New York. 1955. 

 Chemistry and Methods of Enzymes, by J. B. 

 Sumner and F. G. Somers; New York, 1953. 



